Density of creosote treated timber

[PMR06]

What is a good value to use for the density of existing (30 yr old) creosote treated railroad ties, beams, piles, etc?

Thanks in advance.

 

[Ron]

PMR06...due to the weathering and fissures that develop in these, it is difficult to generalize. I would suggest testing a few (bulk specific gravity method) and averaging them.

 

[PMR06]

I am putting together a bridge demo plan and need to estimate the weight of chunks that get lifted off. That way the contractor can roughly know what to expect, make sure he's ok with the crane charts, rigging, etc.

I think I'll start with 60 pcf... unless someone has a reference otherwise.

The contractor will know with the first pick how close we estimate. We can always bite off smaller chunks if the actual timber is heavier.

 

[Ron]

I'd probably go a bit higher. I doubt that they would float, so their unit weight should be greater than water. What about 75 pcf?

 

[SlideRuleEra]

When wood (usually southern pine) was creosoted, the retention of creosote (lb/ft3) was specified. A minimum quantity (for items like posts and railroad crossties was typically about 7 lb/ft3.
For lumber, about 10 lb/ft3.
Piling & structural timber, 12 lb/ft3 (freshwater) and 20 lb/ft3 (saltwater).
In practice, 20 lb/ft3 was almost impossible to reach. Many specifications would permit creosote retention of be "refusal" which was realistically about 18 lb/ft3.

Since southern pine has an accepted density of 45 lb/ft3 (more or less, explaining why some creosoted members would float and others sink) plus adding the retained creosote, I consider your 60 lb/ft3 estimate to be a reasonable conservative upper limit for (random) 30 year old members. Maybe a little less (say 55 lb/ft3) if there are few piling/structural timbers.

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[PMR06]

Thanks SlideRuleEra. The contractor felt 60 pcf was about right too.

Geometry ended up governing... cutting the bridge into truck bed sized pieces. Our weight estimates could be off significantly and the rigging and crane they plan on using will be fine.